(1) Field of Invention
The present invention relates to obstacle avoidance for robot arms. In particular, the invention relates to a planning approach for obstacle avoidance in complex environments for an articulated redundant robot arm which uses a set of via points surrounding an obstacle as an intermediary point between initial and target arm positions.
(2) Description of Related Art
The future of industrial robots is progressing towards systems that have a great deal of flexibility in handling various tasks in a self-organized manner and yet be safe in performing these tasks. One such task is in the area of intelligent robotic assembly. This task requires the robot to reach and grasp complex objects and manipulate them. The robot must be able to reach for any point in its workspace from any other point with varying speed requirements, while avoiding collisions with objects in the environment. The robot must be able to tolerate unexpected contingencies and perform reliably despite changes in sensor geometry and joint mobility. In order to perform these actions in a complex obstacle environment, the robot needs to be both flexible and intelligent.
Simple reactive controllers as known in the art and described in [2-4] (see List of Cited References in the Detailed Description section below) are inadequate for the abovementioned tasks. These systems lack the flexibility to deal with the unexpected contingencies of a complex and changing environment. The closest related art is described in [1]. This related art is bio-inspired and explicitly addresses the obstacle avoidance problem in complex environments. The approach in [1] performs a random exploration of arm movements “mentally” using robot models and each generated arm configuration is evaluated for its ability to bring the arm closer to target while avoiding obstacles. If none of the random movements from the present configuration are successful, then the system “backtracks” to the previous configuration and the search process is continued. The need to backtrack whenever the system reaches an impasse makes it both inefficient and impractical. Furthermore, the system in [1] is very jerky in its movement, and it is unclear as to whether movement smoothing could be applied to the system while still being able to avoid collisions.
Thus, a continuing need exists for a planning approach for obstacle avoidance for a robot arm that can generate and explore possible trajectories around obstacles before executing arm movement, and can then execute successful trajectories in a smooth and fluid manner.